Posts Tagged 'Baltic'

Multi-proxy record of the mid-Maastrichtian event in the European Chalk Sea: paleoceanographic implications

Published 13 December 2023 Science Closed
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The Cretaceous provides us with an excellent case history of ocean-climate-biota system perturbations. Such perturbations occurred several times during the Cretaceous, such as oceanic anoxic events and the end-Cretaceous mass extinction, which have been the subject of an abundant literature. Other perturbations, such as the mid-Maastrichtian Event (MME) remain poorly understood. The MME was associated with global sea-level rise, changes in climate and deep-water circulation that were accompanied by biotic extinctions including “true” inoceramids and the demise of the Caribbean-Tethyan rudist reef ecosystems. So far, the context and causes behind the MME remain poorly studied. We conducted high-resolution integrated biotic, petrological and geochemical studies in order to fill this knowledge gap. We studied, in particular, carbonate Nd and Os isotopes, whole-rock Hg, C and N content, C and N isotopes in organic matter, SCAS isotopes, along with C and O isotopes from foraminifera from the European Chalk Sea: the Polanówka UW-1 core from Poland and the Stevns-1 core from Denmark. Our data showed that sea-level rise of ∼50-100 m lasted around ∼2 Ma and co-occurred with anomalously high mercury concentration. Along with previously published data, our results strongly suggest that the MME was driven by intense volcanic–tectonic activity, likely related to the production of vast oceanic plateaus (LIP, Large Igneous Province). The collapse of reef ecosystems could have been the consequence of LIP-related environmental stress factors, including climate warming, presumably caused by emission of greenhouse gases, modification of the oceanic circulation, oceanic acidification and/or toxic metal input. The disappearance of the foraminifer Stensioeina lineage on the European shelf was likely caused by the collapse of primary production triggered by sea-level rise and limited amount of nutrient input. Nd isotopes and foraminiferal assemblages attest for changes in sea-water circulation in the European Shelf and the increasing contribution of North Atlantic water masses.

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Warming, not acidification, favours survival of non-indigenous over native gammarid species

Published 27 November 2023 Science Closed
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Anthropogenic disturbances, including non-indigenous species (NIS) and climate change, have considerably affected ecosystems and socio-economies globally. Despite the widely acknowledged individual roles of NIS and global warming in biodiversity change, predicting the connection between the two still remains a fundamental challenge and requires urgent attention due to a timely importance for proper conservation management. To improve our understanding of the interaction between climate change and NIS on biological communities, we conducted laboratory experiments to test the temperature and pCO2 tolerance of four gammarid species: two native Baltic Sea species (Gammarus locusta and G. salinus), one Ponto‐Caspian NIS (Pontogammarus maeoticus) and one North American NIS (Gammarus tigrinus). Our results demonstrated that an increase in pCO2 level was not a significant driver of mortality, neither by itself nor in combination with increased temperature, for any of the tested species. However, temperature was significant, and differentially affected the tested species. The most sensitive was the native G. locusta which experienced 100% mortality at 24 °C. The second native species, G. salinus, performed better than G. locusta, but was still significantly more sensitive to temperature increase than either of the NIS. In contrast, NIS performed better than native species with warming, whereby particularly the Ponto-Caspian P. maeoticus did not demonstrate any difference in its performance between the temperature treatments. With the predicted environmental changes in the Baltic Sea, we may expect shifts in distributions of native taxa towards colder areas, while their niches might be filled by NIS, particularly those from the Ponto-Caspian region. Although, northern colder areas may be constrained by lower salinity. Additional studies are needed to confirm our findings across other NIS, habitats and regions to make more general inferences.

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Autonomous high-frequency time-series observations of total alkalinity in dynamic estuarine waters

Published 27 November 2023 Science Closed
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Total alkalinity (TA) is a variable that reflects the acid buffering capacity of seawater, and is key to studies of the global carbon cycle. Daily and seasonal TA variations are poorly constrained due to limitations in observational techniques, and this hampers our understanding of the carbonate system. High quality and high temporal resolution TA observations are required to constrain the controlling factors on TA. Estuarine and coastal waters usually have low TA values and may experience enhanced remineralization of organic matter in response to processes such as eutrophication and terrestrial organic matter input. Therefore, these waters are considered vulnerable to acidification as a consequence of ongoing atmospheric anthropogenic carbon dioxide uptake. An In Situ Analyzer for seawater Total Alkalinity (ISA-TA) was deployed for the first time in low salinity, dynamic estuarine waters (Kiel Fjord, southwestern Baltic Sea). The ISA-TA and a range of additional sensors (for pH, pCO2, nitrate and temperature, salinity, dissolved oxygen) used to obtain ancillary data to interpret the TA variability, were deployed on a pontoon in the inner Kiel Fjord for approximately four months. Discrete samples (for TA, nutrients including NO3−, soluble reactive phosphorus (SRP) and H4SiO4, chlorophyll a) were collected regularly to validate the ISA-TA and to interpret the TA data. The effects on TA in the study area of nitrate uptake and of other processes such as precipitation, run-off and mixing of different waters were observed. The difference between the TA values measured with the ISA-TA and TA of discretely collected samples measured with the Gran titration method was −2.6 ± 0.9 μmol kg−1 (n = 106), demonstrating that the ISA-TA provides stable and accurate TA measurements in dynamic, low salinity (13.2–20.8), estuarine waters. The TA and ancillary data recorded by the sensor suite revealed that physical mixing was the main factor determining the variability in TA in Kiel Fjord during the study period.

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Causes and consequences of acidification in the Baltic Sea: implications for monitoring and management

Published 6 October 2023 Science Closed
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Increasing atmospheric CO2 drives ocean acidification globally. In coastal seas, acidification trends can however be either counteracted or enhanced by other processes. Ecosystem effects of acidification are so far small in the Baltic Sea, but changes should be anticipated unless CO2 emissions are curbed. Possible future acidification trends in the Baltic Sea, conditional on CO2 emissions, climate change, and changes in productivity, can be assessed by means of model simulations. There are uncertainties regarding potential consequences for marine organisms, partly because of difficulties to assign critical thresholds, but also because of knowledge gaps regarding species’ capacity to adapt. Increased temporal and spatial monitoring of inorganic carbon system parameters would allow a better understanding of current acidification trends and also improve the capacity to predict possible future changes. An additional benefit is that such measurements also provide quantitative estimates of productivity. The technology required for precise measurements of the inorganic carbon system is readily available today. Regularly updated status evaluations of acidification, and the inorganic carbon system in general, would support management when assessing climate change effects, eutrophication or characteristics of the pelagic habitats. This would, however, have to be based on a spatially and temporally sufficient monitoring program.

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The benthic-pelagic coupling affects the surface water carbonate system above groundwater-charged coastal sediments

Published 15 September 2023 Science Closed
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Submarine groundwater discharge (SGD) can be a significant source of dissolved nutrients, inorganic and organic carbon, and trace metals in the ocean and therefore can be a driver for the benthic-pelagic coupling. However, the influence of hypoxic or anoxic SGD on the carbonate system of coastal seawater is still poorly understood. In the present study, the production of dissolved inorganic carbon (DIC) and alkalinity (AT) in coastal sediments has been investigated under the impact of oxygen-deficient SGD and was estimated based on the offset between the measured data and the conservative mixing of the end members. Production of AT and DIC was primarily caused by denitrification and sulphate reduction. The AT and DIC concentrations in SGD decreased by approximately 32% and 37% mainly due to mixing with seawater counterbalanced by reoxidation and CO2 release into the atmosphere. Total SGD-AT and SGD-DIC fluxes ranged from 0.1 to 0.2mol m-2 d-1 and from 0.2 to 0.3mol m-2 d-1, respectively. These fluxes are probably the reason why the seawater in the Bay of Puck is enriched in AT and DIC compared to the open waters of the Baltic Sea. Additionally, SGD had low pH and was undersaturated with respect to the forms of the aragonite and calcite minerals of CaCO3. The seawater of the Bay of Puck also turned out to be undersaturated in summer (Inner Bay) and fall (Outer Bay). We hypoth​e​size that SGD can potentially contribute to ocean acidification and affect the functioning of the calcifying invertebrates.

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Species-specific responses of macrophyte production to the increasing CO2 environment with potential ecosystem implications involved in the Baltic Sea

Published 21 August 2023 Science Closed
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Macrophytes vary in their ability to utilize carbon in the form of HCO3− and/or CO2 for photosynthesis. Some functional groups that solely use CO2 for photosynthesis could receive competitive advantages from the predicted increase in CO2 compared to groups with efficient carbon acquisition strategies of HCO3−. The aim of this study was to identify carbon use strategies in the common macrophytes (macroalgae, charophytes, seagrass, and other angiosperms) that represent a broad range of functional traits to CO2 concentrations in the northeastern Baltic Sea. Mechanistic assessment of the carbon physiology of macrophytes was used to predict productivity and competitive interactions between different functional groups under future climate. Carbon use strategies in macrophytes were determined by analysing the carbon isotopes (δ13C), pH drift experiments, and photosynthesis versus dissolved inorganic carbon. In addition, habitat mapping data was used to interpret the potential implications of the elevated CO2 to this coastal ecosystem. The results suggested that the primary productivity of macrophytes is often limited by carbon availability, and the increasing CO2 concentrations in the brackish Baltic Sea are expected to enhance photosynthetic production. While all species tested showed evidence of carbon concentrating mechanisms (CCMs), differential levels of CCM activity indicate varying levels of competitive fitness in a future high-CO2 environment. Overall, macrophytes which inhabit the shallowest and deepest parts of the vegetated zone are expected to experience physiological benefits under future CO2 conditions, while intermediate communities dominated by the perennial brown alga Fucus vesiculosus may experience loss of fitness. These fitness differences have implications for competitive interaction and species range under future climate.

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Anthropogenic and ecology research indicators of top commercial fish species in the Baltic Sea: review

Published 19 June 2023 Science Closed
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In many parts of the world, morality caused as a result of fishing actives is the only influencer affecting the status of top commercial stocks. This however is not the case in the Baltic Sea, which has a multitude of other processes that influence fish stock dynamics. This paper compartmentalises 248 publications that consider the cumulative effects and trade-offs some of the biggest anthropogenic and ecology stressors (temperature change, hypoxia, eutrophication, nutrient pollution acidification, low salinity and food-web dynamics) have on the ecology of top commercial fish species in the Baltic Sea (cod, sprat, whiting, herring, flounder and plaice). The results illustrate the extent of academic research that can be applied to commercial fisheries knowledge in the Baltic Sea and identifies which pressures have the greatest negative impacts for which species. In addition, the findings demonstrate how well individual fish stocks have adapted to the changing environmental conditions of the Baltic Sea. In doing so, the review illustrates the next challenges and underlines what fish will likely dominate in the future and which will struggle. With increased natural hazards, top commercial fish species have reacted differently, depending on the region and adaptive capabilities. In most cases, species in the Clupeidae family have adapted the best to their new surroundings, flatfish resilience is varied, whilst fish in the Gadidae family are finding the Baltic Sea too hostile.

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The impact of potential leakage from the sub-seabed CO2 storage site on the phosphorus transformation in marine sediments – an experimental study

Published 10 May 2023 Science Closed
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Highlights

  • The goal was to study the effect of CO2 leakage from a sub-seabed storage on P pools.
  • We conducted series of experiments exposing sediments to CO2-enriched seawater.
  • Acidification can reduce the efficiency of the burial of P in marine sediments.
  • Under acidic pH, apatite P is transformed into organic and non-apatite inorganic P.

Abstract

Carbon Capture and Storage (CCS) in the sub-seabed geological formations is a method of mitigation of carbon dioxide (CO2) emissions to avoid anthropogenic climate change. While CCS can be one of the most promising technologies to reduce atmospheric CO2 in the short and medium term, it raises serious concerns about the potential leakage of gas from storage sites. In the present study, the impact of acidification induced by CO2 leakage from a sub-seabed storage site on geochemical pools, and thus the mobility, of phosphorus (P) in sediment was investigated during laboratory experiments. The experiments were conducted in a hyperbaric chamber at a hydrostatic pressure of 900 kPa, which simulates pressure conditions at a potential sub-seabed CO2 storage site in the southern Baltic Sea. We performed three separate experiments in which the partial pressure of CO2 was: 352 μatm (corresponding pH = 7.7); 1815 μatm (corresponding pH = 7.0), and 9150 μatm (corresponding pH = 6.3). Under pH 7.0 and 6.3, apatite P is transformed into organic and non-apatite inorganic forms, which are less stable than Casingle bondP bonds and can be more easily released into the water column. At pH 7.7, P released during mineralization of organic matter and microbial reduction of Fesingle bondP phases is bound with Ca, and the concentration of this form increases. The obtained results indicate that acidification of bottom water can reduce the efficiency of P burial in marine sediments, which contributes to an increase in P concentration in the water column and promote eutrophication especially in shallow areas.

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Marked recent declines in boron in Baltic Sea cod otoliths – a bellwether of incipient acidification in a vast hypoxic system?

Published 11 April 2023 Science Closed
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Ocean acidification is spreading globally as a result of anthropogenic CO2 emissions, but the Baltic Sea has until recently been thought to be relatively well-buffered by terrigenous inputs of alkalinity from its watershed. We discovered a 3- to 5-fold decline in boron (as B : Ca) in otoliths of eastern Baltic Sea cod (EBC) between the late 1990s and 2021. B : Ca is positively proportional to pH in carbonates, as B in the form of borate is taken up in the CaCO3 matrix. Examining a time series of EBC otoliths, we found varying levels of B : Ca since the 1980s, with the most recent years at an all-time low during this period. This trend correlates with declines in pH and dissolved oxygen, but not with changes in salinity. We examined possible physiological influences on B : Ca by including a collection of healthy Icelandic cod as an out-group. Icelandic cod otoliths showed strongly positive correlations of B : Ca with physiologically regulated P : Ca; this was not the case for EBC. Finally, B : Ca in EBC otoliths is anti-correlated to some extent with Mn : Mg, a proposed proxy for hypoxia exposure. This negative relationship is hypothesized to reflect the dual phenomena of hypoxia and acidification as a result of decomposition of large algal blooms. Taken together, the otolith biomarkers Mn : Mg and B : Ca suggest a general increase in both hypoxia and acidification within the Baltic intermediate and deep waters in the last decade reflected in cod otoliths.

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The history of chemical concepts and field studies of CO2 in seawater: a tribute to Kurt Buch (1881–1967)

Published 25 January 2023 Science Closed
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This review of the research on the marine CO2 system spans the time between the mid-19th century and the first years after World War II. It covers the period from the first attempts to determine the amount of CO2 dissolved in seawater to the first complete physico-chemical characterization of the marine CO2 system. The development of the latter was significantly influenced by the theoretical and experimental work of the Finnish chemical oceanographer Kurt Buch (1881–1967) during the first half of the 20th century. To acknowledge his outstanding achievements in Chemical Oceanography, this review is dedicated to him.

The first part of our discussion is organized along the characteristic variables of the marine CO2 system. The analytical procedures that led successively to the definition of total CO2, alkalinity (“neutral carbonate”), the CO2 partial pressure (“CO2 tension”) and pH are briefly described. We trace the attempts to connect these variables quantitatively through the mass action law. After several failed attempts, CO2 dissociation constants were finally determined with the support of the International Council for the Exploration of the Sea (1931). Their results constituted the basis of the marine CO2 studies conducted after World War II.

The second focus of our review refers to the various field studies, including early measurements of total CO2 and alkalinity during Norwegian (1878) and Danish expeditions (1895/96) in the North Atlantic and Arctic Ocean and the first measurements of surface water pCO2 in the North Atlantic, in 1902. Furthermore, we acknowledge the achievements of the German Atlantic expedition (1925–1927) for the characterization of the vertical and horizontal distribution of pH, pCO2 and CaCO3 saturation in the Atlantic Ocean. Among Buch’s field studies of the CO2 system, we consider the Finnish monitoring program, in which pH and alkalinity were measured at over 70 stations in the northern Baltic Sea.

Whenever it is appropriate, we show the connection between past scientific ideas, concepts and knowledge with current efforts and developments concerning the understanding of the marine carbon cycle and its response to increasing atmospheric CO2.

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Global climate change and the Baltic Sea ecosystem: direct and indirect effects on species, communities and ecosystem functioning

Published 13 April 2022 Science Closed
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Climate change has multiple effects on Baltic Sea species, communities and ecosystem functioning through changes in physical and biogeochemical environmental characteristics of the sea. Associated indirect and secondary effects on species interactions, trophic dynamics and ecosystem function are expected to be significant. We review studies investigating species-, population- and ecosystem-level effects of abiotic factors that may change due to global climate change, such as temperature, salinity, oxygen, pH, nutrient levels, and the more indirect biogeochemical and food web processes, primarily based on peer-reviewed literature published since 2010.

For phytoplankton, clear symptoms of climate change, such as prolongation of the growing season, are evident and can be explained by the warming, but otherwise climate effects vary from species to species and area to area. Several modelling studies project a decrease of phytoplankton bloom in spring and an increase in cyanobacteria blooms in summer. The associated increase in N:P ratio may contribute to maintaining the “vicious circle of eutrophication”. However, uncertainties remain because some field studies claim that cyanobacteria have not increased and some experimental studies show that responses of cyanobacteria to temperature, salinity and pH vary from species to species. An increase of riverine dissolved organic matter (DOM) may also decrease primary production, but the relative importance of this process in different sea areas is not well known. Bacteria growth is favoured by increasing temperature and DOM, but complex effects in the microbial food web are probable. Warming of seawater in spring also speeds up zooplankton growth and shortens the time lag between phytoplankton and zooplankton peaks, which may lead to decreasing of phytoplankton in spring. In summer, a shift towards smaller-sized zooplankton and a decline of marine copepod species has been projected.

In deep benthic communities, continued eutrophication promotes high sedimentation and maintains good food conditions for zoobenthos. If nutrient abatement proceeds, improving oxygen conditions will first increase zoobenthos biomass, but the subsequent decrease of sedimenting matter will disrupt the pelagic–benthic coupling and lead to a decreased zoobenthos biomass. In the shallower photic systems, heatwaves may produce eutrophication-like effects, e.g. overgrowth of bladderwrack by epiphytes, due to a trophic cascade. If salinity also declines, marine species such as bladderwrack, eelgrass and blue mussel may decline. Freshwater vascular plants will be favoured but they cannot replace macroalgae on rocky substrates. Consequently invertebrates and fish benefiting from macroalgal belts may also suffer. Climate-induced changes in the environment also favour establishment of non-indigenous species, potentially affecting food web dynamics in the Baltic Sea.

As for fish, salinity decline and continuing of hypoxia is projected to keep cod stocks low, whereas the increasing temperature has been projected to favour sprat and certain coastal fish. Regime shifts and cascading effects have been observed in both pelagic and benthic systems as a result of several climatic and environmental effects acting synergistically.

Knowledge gaps include uncertainties in projecting the future salinity level, as well as stratification and potential rate of internal loading, under different climate forcings. This weakens our ability to project how pelagic productivity, fish populations and macroalgal communities may change in the future. The 3D ecosystem models, food web models and 2D species distribution models would benefit from integration, but progress is slowed down by scale problems and inability of models to consider the complex interactions between species. Experimental work should be better integrated into empirical and modelling studies of food web dynamics to get a more comprehensive view of the responses of the pelagic and benthic systems to climate change, from bacteria to fish. In addition, to better understand the effects of climate change on the biodiversity of the Baltic Sea, more emphasis should be placed on studies of shallow photic environments.

The fate of the Baltic Sea ecosystem will depend on various intertwined environmental factors and on development of the society. Climate change will probably delay the effects of nutrient abatement and tend to keep the ecosystem in its “novel” state. However, several modelling studies conclude that nutrient reductions will be a stronger driver for ecosystem functioning of the Baltic Sea than climate change. Such studies highlight the importance of studying the Baltic Sea as an interlinked socio-ecological system.

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Carbonate chemistry in the microenvironment within cyanobacterial aggregates under present-day and future pCO2 levels

Published 29 December 2021 Science Closed
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Photosynthesis and respiration cause distinct chemical microenvironments within cyanobacterial aggregates. Here, we used microsensors and a diffusion–reaction model to characterize gradients in carbonate chemistry and investigate how these are affected by ocean acidification in Baltic vs. Pacific aggregates (Nodularia and Dolichospermum vs. Trichodesmium). Microsensor measurements of O2 and pH were performed under in situ and expected future pCO2 levels on Nodularia and Dolichospermum aggregates collected in the Baltic Sea. Under in situ conditions, O2 and pH levels within the aggregates covered ranges of 80–175% air saturation and 7.7–9.4 in dark and light, respectively. Carbon uptake in the light was predicted to reduce HCO3− by 100–150 μmol L−1 and CO2 by 3–6 μmol L−1 in the aggregate center compared to outside, inducing strong CO2 depletion (down to 0.5 μmol L−1 CO2 remaining in the center) even when assuming that HCO3− covered 80–90% of carbon uptake. Under ocean acidification conditions, enhanced CO2 availability allowed for significantly lower activity of carbon concentrating mechanisms, including a reduction of the contribution of HCO3− to carbon uptake by up to a factor of 10. The magnification of proton gradients under elevated pCO2 that was predicted based on a lower buffer capacity was observed in measurements despite a concurrent decrease in photosynthetic activity. In summary, we provide a quantitative image of the inorganic carbon environment in cyanobacterial aggregates under present-day and expected future conditions, considering both the individual and combined effects of the chemical and biological processes that shape these environments.

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Reagentless acid–base titration for alkalinity detection in seawater

Published 9 November 2021 Science Closed
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Herein, we report on a reagentless electroanalytical methodology for automatized acid–base titrations of water samples that are confined into very thin spatial domains. The concept is based on the recent discovery from our group (Wiorek, A. Anal. Chem. 2019, 91, 14951−14959), in which polyaniline (PANI) films were found to be an excellent material to release a massive charge of protons in a short time, achieving hence the efficient (and controlled) acidification of a sample. We now demonstrate and validate the analytical usefulness of this approach with samples collected from the Baltic Sea: the titration protocol indeed acts as an alkalinity sensor via the calculation of the proton charge needed to reach pH 4.0 in the sample, as per the formal definition of the alkalinity parameter. In essence, the alkalinity sensor is based on the linear relationship found between the released charge from the PANI film and the bicarbonate concentration in the sample (i.e., the way to express alkalinity measurements). The observed alkalinity in the samples presented a good agreement with the values obtained by manual (classical) acid–base titrations (discrepancies <10%). Some crucial advantages of the new methodology are that titrations are completed in less than 1 min (end point), the PANI film can be reused at least 74 times over a 2 week period (<5% of decrease in the released charge), and the utility of the PANI film to even more decrease the final pH of the sample (pH ∼2) toward applications different from alkalinity detection. Furthermore, the acidification can be accomplished in a discrete or continuous mode depending on the application demands. The new methodology is expected to impact the future digitalization of in situ acid–base titrations to obtain high-resolution data on alkalinity in water resources.

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Composition and dominance of edible and inedible phytoplankton predict responses of Baltic Sea summer communities to elevated temperature and CO2

Published 8 November 2021 Science Closed
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Previous studies with Baltic Sea phytoplankton combining elevated seawater temperature with CO2 revealed the importance of size trait-based analyses, in particular dividing the plankton into edible (>5 and <100 µm) and inedible (<5 and >100 µm) size classes for mesozoopankton grazers. While the edible phytoplankton responded predominantly negative to warming and the inedible group stayed unaffected or increased, independent from edibility most phytoplankton groups gained from CO2. Because the ratio between edible and inedible taxa changes profoundly over seasons, we investigated if community responses can be predicted according to the prevailing composition of edible and inedible groups. We experimentally explored the combined effects of elevated temperatures and CO2 concentrations on a late-summer Baltic Sea community. Total phytoplankton significantly increased in response to elevated CO2 in particular in combination with temperature, driven by a significant gain of the inedible <5 µm fraction and large filamentous cyanobacteria. Large flagellates disappeared. The edible group was low as usual in summer and decreased with both factors due to enhanced copepod grazing and overall decline of small flagellates. Our results emphasize that the responses of summer communities are complex, but can be predicted by the composition and dominance of size classes and groups.

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Pulsed pressure: fluctuating impacts of multifactorial environmental change on a temperate macroalgal community

Published 1 November 2021 Science Closed
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Global change impacts marine organisms and communities mainly through ocean warming, acidification, deoxygenation, and changes in nutrient inputs and water circulation. To assess the ecological impacts of global change, the effects of multiple interacting environmental drivers, including their fluctuations, should be tested at different levels of biological organization. In an outdoor mesocosm study, we investigated the differential effects of three simulated upwelling events coupled with ocean warming (1–5°C above ambient) on a temperate benthic community in the Western Baltic Sea. Ocean warming, especially in summer when temperatures are close to or above the physiological optimum of many species, is likely to impose thermal stress with species-specific impacts. As the properties of deep water vary seasonally, so will the effects of upwelling. Upwelling of cooler deep water in midsummer may alleviate thermal stress, although this mitigation may be modulated by upwelling-associated shifts in other water-quality parameters such as salinity, nutrients, or late-summer hypoxia. This investigation showed that in the Western Baltic Ocean warming was rather beneficial in early and late summer but detrimental when ambient temperatures were highest in midsummer. The effects of upwelling in the absence of ocean warming were generally weakly beneficial, while this effect tended to vanish with intensifying imposed ocean warming. Hypoxia associated with the late summer upwelling impacted some of the grazer species but did not impact the macroalgae. We conclude that in coastal temperate benthic communities, ocean warming is the predominant stressor that may partially and seasonally be buffered by upwelling.

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Effects of seawater scrubbing on a microplanktonic community during a summer-bloom in the Baltic Sea

Published 29 September 2021 Science Closed
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Highlights

  • Effects of seawater scrubbing on a microplanktonic community were assessed.
  • Biovolume increased with increasing concentrations of scrubber discharge water.
  • Group-specific impacts were recorded.
  • pH alone could not explain the observed results.
  • Other stressors in the scrubber water were responsible for the observed effect.

Abstract

The International Maritime Organization (IMO) has gradually applied stricter regulations on the maximum sulphur content permitted in marine fuels and from January 1, 2020, the global fuel sulphur limit was reduced from 3.5% to 0.5%. An attractive option for shipowners is to install exhaust gas cleaning systems, also known as scrubbers, and continue to use high sulphur fuel oil. In the scrubber, the exhausts are led through a fine spray of water, in which sulphur oxides are easily dissolved. The process results in large volumes of acidic discharge water, but while regulations are focused on sulphur oxides removal and acidification, other pollutants e.g. polycyclic aromatic hydrocarbons, metals and nitrogen oxides can be transferred from the exhausts to the washwater and discharged to the marine environment. The aim of the current study was to investigate how different treatments of scrubber discharge water (1, 3 and 10%) affect a natural Baltic Sea summer microplanktonic community. To resolve potential contribution of acidification from the total effect of the scrubber discharge water, “pH controls” were included where the pH of natural sea water was reduced to match the scrubber treatments. Biological effects (e.g. microplankton species composition, biovolume and primary productivity) and chemical parameters (e.g. pH and alkalinity) were monitored and analysed during 14 days of exposure. Significant effects were observed in the 3% scrubber treatment, with more than 20% increase in total biovolume of microplankton compared to the control group, and an even greater effect in the 10% scrubber treatment. Group-specific impacts were recorded where diatoms, flagellates incertae sedis, chlorophytes and ciliates increased in biovolume with increasing concentrations of scrubber water while no effect was recorded for cyanobacteria. In contrast, these effects was not observed in the “pH controls”, a suggestion that other parameters/stressors in the scrubber water were responsible for the observed effects.

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Ocean acidification (OA) in the Baltic Sea from a Swedish perspective

Published 27 September 2021 Newsletters and reports Closed
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Background
This report is produced as part of the project “Baltic Sea Acidification Mitigation” (BALSAM), supported by the Swedish Institute. The aim of this report and other, corresponding reports (produced for the other countries participating in BALSAM) is primarily to inform environmental NGOs and other stakeholders interested in environmental issues. The aim of this country report is to provide information on Ocean Acidification (OA) in the Baltic Sea with special emphasis on Swedish waters, and to provide an insight into the research and monitoring that are the basis of the current understanding of OA in these waters. This is done as support for campaigning towards mitigation of greenhouse gases and protection of the seas. Whereas this document is not a comprehensive literature review, it is intended as a timely guide to the concept of OA, and does contain key publications and links to further indepth reading and sources of additional information.

Introduction
Ocean acidification (OA) comes in the wake of climate change as the result of increased atmospheric CO2, which is taken up by the oceans. About 30 % of the CO2 that is emitted to the atmosphere because of human activity ends up in the waterbodies. Part of the CO2 reacts with water, and forms carbonic acid. Some of the carbonic acid dissociates, resulting in bicarbonate and in hydrogen ions. This process leads to acidification (lower pH, i.e. higher concentration of hydrogen ions). Organisms in the oceans are adapted to the pH-conditions that have prevailed in the seas prior to this human driven acidification-process. Especially calcifying organisms are sensitive to acidification, but the physiology of many other organisms can be affected as well, as can the complex ecological interactions between organisms. In a global setting, ongoing and projected effects of OA have been extensively described in several IPCC reports (e.g. IPCC, 2018, 2019).

In Sweden, an interdisciplinary review on causes and consequences of OA in the Swedish Seas (including both the Baltic Sea and the more saline waters of Skagerrak at the Swedish west coast), as well as knowledge gaps, was published relatively recently as part of work supported by the Royal Swedish Academy of Sciences (Havenhand et al. 2017). Additionally, in the same context, a scientific review focusing on the ecological consequences of OA was published by Havenhand et al. in 2019. A policy brief1 on OA in the Baltic Sea was furthermore published in 2020 by The Baltic Sea Centre of Stockholm University (Gustafsson & Winder 2020). This policy brief provides a general view of OA as support for policy making.

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Cyanobacteria net community production in the Baltic Sea as inferred from profiling pCO2 measurements

Published 10 September 2021 Science Closed
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Organic matter production by cyanobacteria blooms is a major environmental concern for the Baltic Sea, as it promotes the spread of anoxic zones. Partial pressure of carbon dioxide (pCO2) measurements carried out on Ships of Opportunity (SOOP) since 2003 have proven to be a powerful tool to resolve the carbon dynamics of the blooms in space and time. However, SOOP measurements lack the possibility to directly constrain depth-integrated net community production (NCP) in moles of carbon per surface area due to their restriction to the sea surface. This study tackles the knowledge gap through (1) providing an NCP best guess for an individual cyanobacteria bloom based on repeated profiling measurements of pCO2 and (2) establishing an algorithm to accurately reconstruct depth-integrated NCP from surface pCO2 observations in combination with modelled temperature profiles.

Goal (1) was achieved by deploying state-of-the-art sensor technology from a small-scale sailing vessel. The low-cost and flexible platform enabled observations covering an entire bloom event that occurred in July–August 2018 in the Eastern Gotland Sea. For the biogeochemical interpretation, recorded pCO2 profiles were converted to C∗T, which is the dissolved inorganic carbon concentration normalised to alkalinity. We found that the investigated bloom event was dominated by Nodularia and had many biogeochemical characteristics in common with blooms in previous years. In particular, it lasted for about 3 weeks, caused a C∗T drawdown of 90 µmol kg−1, and was accompanied by a sea surface temperature increase of 10 ∘C. The novel finding of this study is the vertical extension of the C∗T drawdown up to the compensation depth located at around 12 m. Integration of the C∗T drawdown across this depth and correction for vertical fluxes leads to an NCP best guess of ∼1.2 mol m−2 over the productive period.

Addressing goal (2), we combined modelled hydrographical profiles with surface pCO2 observations recorded by SOOP Finnmaid within the study area. Introducing the temperature penetration depth (TPD) as a new parameter to integrate SOOP observations across depth, we achieve an NCP reconstruction that agrees to the best guess within 10 %, which is considerably better than the reconstruction based on a classical mixed-layer depth constraint.

Applying the TPD approach to almost 2 decades of surface pCO2 observations available for the Baltic Sea bears the potential to provide new insights into the control and long-term trends of cyanobacteria NCP. This understanding is key for an effective design and monitoring of conservation measures aiming at a Good Environmental Status of the Baltic Sea.

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Cellular level response of the bivalve Limecola balthica to seawater acidification due to potential CO2 leakage from a sub-seabed storage site in the southern Baltic Sea: TiTank experiment at representative hydrostatic pressure

Published 28 June 2021 Science Closed
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Highlights

  • Cellular level responses of L. balthica to acidification caused by CO2 was tested 9 ATM pressure.
  • The bivalve is tolerant to medium-term severe environmental hypercapnia.
  • Seawater pH 7.0 induced effects on radical defence mechanisms (GPx, GST, CAT).
  • pH 6.3 caused increased cellular oxidative stress (MDA) and detoxification (tGST).

Abstract

Understanding of biological responses of marine fauna to seawater acidification due to potential CO2 leakage from sub-seabed storage sites has improved recently, providing support to CCS environmental risk assessment. Physiological responses of benthic organisms to ambient hypercapnia have been previously investigated but rarely at the cellular level, particularly in areas of less common geochemical and ecological conditions such as brackish water and/or reduced oxygen levels. In this study, CO2-related responses of oxygen-dependent, antioxidant and detoxification systems as well as markers of neurotoxicity and acid-base balance in the Baltic clam Limecola balthica from the Baltic Sea were quantified in 50-day experiments. Experimental conditions included CO2 addition producing pH levels of 7.7, 7.0 and 6.3, respectively and hydrostatic pressure 900 kPa, simulating realistic seawater acidities following a CO2 seepage accident at the potential CO2-storage site in the Baltic. Reduced pH interfered with most biomarkers studied, and modifications to lactate dehydrogenase and malate dehydrogenase indicate that aerobiosis was a dominant energy production pathway. Hypercapnic stress was most evident in bivalves exposed to moderately acidic seawater environment (pH 7.0), showing a decrease of glutathione peroxidase activity, activation of catalase and suppression of glutathione S-transferase activity likely in response to enhanced free radical production. The clams subjected to pH 7.0 also demonstrated acetylcholinesterase activation that might be linked to prolonged impact of contaminants released from sediment. The most acidified conditions (pH 6.3) stimulated glutathione and malondialdehyde concentration in the bivalve tissue suggesting potential cell damage. Temporal variations of most biomarkers imply that after a 10-to-15-day initial phase of an acute disturbance, the metabolic and antioxidant defence systems recovered their capacities.

Continue reading ‘Cellular level response of the bivalve Limecola balthica to seawater acidification due to potential CO2 leakage from a sub-seabed storage site in the southern Baltic Sea: TiTank experiment at representative hydrostatic pressure’

The CO2 system dynamics in the vicinity of the vistula river mouth (the southern Baltic Sea): a baseline investigation

Published 4 June 2021 Science Closed
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Highlights

  • The CO2 system in the Vistula River plume was investigated for the first time.
  • Vistula River as an important TA source to the Baltic Sea.
  • OM production and remineralization affect the CO2 system in the Vistula River plume.
  • The variability of pH and Ω in the Vistula River plume were significant.
  • Vistula River is a source of PIC to the Gdańsk Bay.

Abstract

The CO2 system dynamics in coastal areas strongly controlled by river outflow is largely understudied. In this study, the influence of a large, continental, carbonate-rich river on the carbonate system was seasonally examined in the vicinity of the Vistula River Mouth. Three parameters describing the CO2 system were investigated: the partial pressure of carbon dioxide (pCO2), total alkalinity (TA), and pH, together with salinity, temperature, oxygen concentration, calcium cation (Ca2+), particulate inorganic carbon (PIC), and inorganic carbon (IC) in sediments. TA varied from 1700 μmol kg−1 in the brackish water of the Gdańsk Bay to 3475 μmol kg−1 in the Vistula River plume, highlighting the difference between the two end-members. Highest pCO2 was observed in October (855 μatm) and lowest in May (148 μatm). Oxygen concentration was negatively correlated to pCO2 in all seasons, suggesting that both were inversely controlled by the net ecosystem production (NEP). The pH seasonal variation was significant with a range of 0.72 unit. The calcium carbonate saturation (Ω) varied from 0.8 to 8.5 for calcite and from 0.5 to 8.5 for aragonite, both displaying Ω < 1 in February 2018.

This study shows the importance of ecosystem metabolism and TA end-member variability (3138–3631 μmol kg−1), for controlling pH in the vicinity of the Vistula River Mouth. In addition, we present data on PIC, supporting possible deposition of inorganic forms of carbon to the sediments near the Vistula River Mouth.

Continue reading ‘The CO2 system dynamics in the vicinity of the vistula river mouth (the southern Baltic Sea): a baseline investigation’

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